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Old 03-05-2018, 08:41 PM   #1
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Galvanic corrosion on aluminum floor?

Iíve searched the forums for info on this subject with no luck. It appears my subfloor is aluminum and not steel! Iíve been so caught up in ripping up the plywood that it didnít even occur to me that this could be the case. There are several holes, presumably due to galvanic corrosion with steel bolts. I was getting ready to use the olí rust-converter-rustoleum-paint technique, but now...what do I do? Fiberglass the holes? Epoxy?


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Old 03-05-2018, 10:46 PM   #2
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Iíve searched the forums for info on this subject with no luck. It appears my subfloor is aluminum and not steel! Iíve been so caught up in ripping up the plywood that it didnít even occur to me that this could be the case. There are several holes, presumably due to galvanic corrosion with steel bolts. I was getting ready to use the olí rust-converter-rustoleum-paint technique, but now...what do I do? Fiberglass the holes? Epoxy?


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Interesting...how would the floor be connected to the bus structure? Not sure if dissimilar metals can be welded... Is it a gillie?

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Old 03-06-2018, 01:43 AM   #3
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So no magnet sticks to the floor? If anything other than wood I would be tempted to epoxy/fiberglass, after cleaning the floor of all loose scale and figure out what coating to put on, then plywood on top of foam board. It'll last a hundred years, if not, ten.

Crowns were aluminum bodied, but the floor was a thick marine-grade plywood, or so I have read (and by looking at a few too.)
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Old 03-07-2018, 08:17 AM   #4
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Iím not sure how itís attached to the chassis, seems like itís riveted? Confirmed that no magnet sticks to the floor. Iím also thinking fibreglass/epoxy.


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Old 03-07-2018, 08:41 AM   #5
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Looks fairly ugly in your pic, how extensive is it? Unfortunately, when aluminum starts to corrode, it won't stop by covering it up with epoxy, or anything else. You must remove the corroded area completely, maybe with a hole saw? Then I would fill the hole with a plywood plug installed wet with epoxy.

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Old 03-07-2018, 08:51 AM   #6
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Iím not sure how itís attached to the chassis, seems like itís riveted? Confirmed that no magnet sticks to the floor. Iím also thinking fibreglass/epoxy.


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So what kind of bus you got? Not only do you need to remove the corroded area completely...if you can, you need to see if you possibly have some kinda electrical issues...that can cause problems...if it's typical road chemical stuff...maybe you could get some zinc blocks to prevent further corrosion...they use them in maritime industry...not totally sure it'd work...check with a maritime outfitter like West marine...

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Old 03-07-2018, 09:01 AM   #7
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So what kind of bus you got? Not only do you need to remove the corroded area completely...if you can, you need to see if you possibly have some kinda electrical issues...that can cause problems...if it's typical road chemical stuff...maybe you could get some zinc blocks to prevent further corrosion...they use them in maritime industry...not totally sure it'd work...check with a maritime outfitter like West marine...

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Sacrificial anodes won't work here. They rely on a complete electrical circuit made by (usually salt) water connecting the anode to the rest of the structure.

When aluminum is used in this kind of structure it is usually isolated from the steel with insulation, often teflon.
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Old 03-07-2018, 09:07 AM   #8
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Sacrificial anodes won't work here. They rely on a complete electrical circuit made by (usually salt) water connecting the anode to the rest of the structure.

When aluminum is used in this kind of structure it is usually isolated from the steel with insulation, often teflon.
Thx...I really didn't know...also the Houston transit buses have to static strips...which is interesting and probably unrelated to the topic

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Old 03-07-2018, 11:43 AM   #9
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If it were me I would cut the edges of the corrosion off and patch panel it with aluminum plate the thickness of the original floor cutting the patches as close to supports and overlapping seams wherever possible instead of mechanical fasteners I would use one of the many panel adhesives I have used Evercote Maxim with good success you will never"feel" the patches once insulated and floored probably not feel them under flooring as long as you don't try to install flooring direct to metal.
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Old 03-07-2018, 02:47 PM   #10
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If it's aluminum, you can patch it using MAPP gas and aluminum brazing rods. No need for a welder since the area is small and doesn't really affect the structure of the bus. I've done it on some trailers and RVs. It's not to difficult.

https://www.amazon.com/Bernzomatic-T...dd626a7e280a81

https://www.amazon.com/2mmx45cm-Alum...02d896d2e780de

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Old 03-07-2018, 04:15 PM   #11
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The patches could be alumabrazed in but is probably not for the novice hang in 1 spot 2 seconds to long and a hole much worse than you had can appear as the parent material disappears in a puddle under the bus, panel adhesive works great no special skills needed.
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Old 03-07-2018, 06:06 PM   #12
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Be careful with the brazing idea if the floor was undercoated at one time or you have any body bushings within inches of the heated area.
If there is undercoating then it might be a good time to inspect it also for problem areas underneath that's not showing up inside.
Just cheek for combustibles on the underside if you go the torch route
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Old 03-07-2018, 06:08 PM   #13
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Iíd be looking for bad grounds for sure

I have seen DC cause severe corrosion in aluminum when a DC has to search for a ground back to the steel frame main battery ground


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